Filament tensioning means for electron discharge devices



March 16, 1954 T H CARLSTRQM 2,672,570

FILAMENT TENSIONING MEANS FOR ELECTRON DISCHARGE DEVICES Filed May 7, 1948 INVENTOR. Thu/'eH Carlsi'rom BYM 'Z .g v

Hitorney Patented Mar. 16, 1954 FILAMENT TENSIONING MEANS FOR ELEC- TRON DISCHARGE DEVICES Thure H. Carlstrom, Hempstead, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application May 7, 1948, Serial No. 25,601

6 Claims. 1

shorting between filament and other electrodes within the tube. Known arrangements for tensioning filaments have a distinct support structure for a tensioning spring. it is especially desirable in subminiature tubes to eliminate excess structure and keep the physical tube and electrode sizes small thus improving the high frequency characteristics. As an example of a prior art practice in mounting tensioning means reference may be had to the pending application of Haas, Serial Number 441,886 in which a distinct supporting structure is supplied for mounting the tensioning spring.

An object of the invention is to provide a filament tensioning means having a minimum of parts and which is of extremely simple arrangement and compact structure. A further object of this invention is to provide a mount for the filament tensioning means which ensures transverse rigidity of the spring. It is a further ob ject of the invention to provide an electron tube including a filamentary cathode which does not change its characteristics under exposure to shock conditions.

In one aspect the invention makes use of an existing member in the tube structure thus eliminating additional structure. A better understanding of the invention and further objects and features of novelty will be afforded by the following detailed description, considered in connection with the accompanying drawing, and those features of the invention which are believed to be novel and patentable are pointed out in the claims appended hereto.

In the drawings:

Figure l is a view in section along line l-I of Figure 2.

Figure 2 is a side elevation partly in section of an electron tube including the invention.

Figure 3 is a view in perspective of a portion 01 an electrode assembly including the filament tensioning means.

Figure 4 is a side elevation of Figure 2 with the envelope removed.

Referring to the drawing, the tube II of Figure 1, comprises an envelope l2, within which there is arranged an electrode assembly l3. The

electrode assembly, used for illustrative purposes, includes a two section anode, having sections Ma, Mb, 2. first grid i5, a second grid l6 and a filamentary cathode H. The first grid I5 is supported upon rods lfla, I 81), and the second grid it is similarly carried by rods Ida, Nib. The electrodes are maintained in spaced relation by Waiers'm and 2! which are apertured to receive grid rods 58a, I81), Illa, I912.

The anode sections are maintained in the electrode assembly it by anode rods 22 and 23 which penetrate apertures in wafers 2i and 2|, and by rods 24 and 25 which penetrate wafer 20. To complete the sturdy structure and connect anode sections Ma and Mb electrically, a bridge member 25 having ends 21 and 28 penetrates wafer 2i and is secured to both anode sections.

The wafers 20 and 2| are each provided with an angular slot for receiving the filamentary cathode ll and with suitable apertures for filament rods Hand 35. An L-shaped bracket 36 is fastened to rod 35. The filamentary cathode is provided with end tabs 3! and 38.

Tab 37, at one extremity of cathode I1, is

fastened to rod 3 while tab 38 at the other end of the cathode is secured to the U-shaped arm 32 of tensioning spring 30. The ends 33a and 33b of the spring are fastened to bracket 36. Each half of spring 30 includes a coil 3| that encircles and is supported by bridge member 26 of the anode. To maintain different voltages on the anode and the cathode, an insulating coating 29 encases bridge member 26 within coils 3| of spring 30. It is to be noted that spring 30 is preformed, and when stressed and attached to bracket 36 and to tab 38 provides proper tension to filament H.

An electric current path for filamentary cathode ll extends through connections between lead We, filament rod 34, and tab 3'! respectively at one end, and tab 38, spring 30, bracket 3%, rod

35 and lead l3b at the other end.

Additional structure for mounting the spring 39 is eliminated by forming the anode bridging member 26 with an insulating cover over which the spring is mounted. Transverse rigidity achieved with the balanced two-coil spring in the aforementioned Haas application is retained in the construction here disclosed.

As I have described a specific embodiment of my invention, it is obvious that modifications may be made without departing from the spirit thereof. Thus the insulated bridge may alternatively support a single-coil tensioning spring; and the coiled spring may be carried by a bridge connecting sections of another electrode such as a multi-part electrostatic shield. The number of electrodes and the shape or size of the slot for the filamentary cathode may be varied.

What is claimed is:

1. An electron discharge device comprising an electrode assembly, said electrode assembly including a filament and a plural section electrode, a bridge member connecting two sections of said electrode, a stop member, an insulating cover over a portion of said bridge member, a tensioning member having an intermediate portion, a pair of helical coils and terminal portion, said helical coils encircling said bridge member and supported on said insulating cover, said terminal portion being secured to said stop member and said filament being in contact with said intermediate portion.

2. An electron discharge device comprising an electrode assembly, said electrode assembly ineluding a filament and a plural section electrode, a bridge member connecting two sections of said electrode, a stop member, a tensioning member having an intermediate portion, a pair of helical coils and terminal portions, said helical coils encircling said bridge member and supported thereby, said terminal portions being secured to said stop member and said filament being secured to said intermediate portion.

3. An electron discharge device comprising an It electrode assembly, said electrode assembly including a filament and a plural section anode, a bridge member connecting two sections of said anode, a stop member, an insulating cover over a portion of said bridge member, a tensioning member having an intermediate portion, a pair of helical coils and terminal portions, said helical coils encircling said bridge member and supported on said insulating cover, said terminal portions being secured to said stop member and said filament being secured to said intermediate portion.

4. A filament support for electron discharge devices including in combination with a filament, a stop member, an arched member, an insulating coating over a portion of said arched member, a tensioning member comprising an intermediate portion, a pair of helical coils and terminal portions, said helical coils encircling said arched member and supported on said insulating cover,

said terminal portions being secured to said stop member, and said filament being in contact with said intermediate portion.

5. An electron discharge device comprising an electrode assembly including a filament and a plural section electrode, a bridge member connecting two sections of said electrode, a stop member, an insulating cover over a portion of said bridge member, a tensioning member having a central U-shaped portion, a pair of helical coils and terminal portions, said helical coils encircling said bridge member and supported on said insulating cover, said terminal portions being secured to said stop member and said filament being secured to the apex of said U-shaped portion.

6. An electron discharge device comprising an electrode assembly including a filament and a plural section anode, a bridge member connecting two sections of said anode, a stop member, an insulating cover over a portion of said bridge member, a tensioning member having a central U-shaped portion, a pair of helical coils and terminal portions, said helical coils encircling said bridge member and supported on said insulating cover, said terminal portions being secured to said stop member and said filament being secured to the apex of said U-shapedportion.

THURE H. CARLSTROM.

No References Cited. 

